The present invention relates to a technology for balancing loads among a plurality of disk storage systems and more particularly to a storage network switch for networking a plurality of computers and a plurality of disk storage systems receiving the load balancing
Most common design of computer systems to the date has been constituted of one host computer with a plurality of disk storage systems. To distribute load balancing among disk storages in such a system, the host computer is in general in charge of balancing. More specifically, in most cases, a program on the host monitors the load of disk storages, and in order to move data for load balancing, a user operates the computer, according to the monitored measurements to manually instruct the data movement.
For example, a typical process of data movement is disclosed in “SPARC & Solaris: performance tuning” by Adrian Cockcroft, Sun Microsystems Japan, Inc. Ed., pp 87 to pp 95, publishedby ASCII, Corp., 1995 (reference 1). In the reference 1, “iostat” program that runs on a host measures the load of the disk storage systems. The load can be determined by measuring the response time of I/O (input/output) commands issued by the program to the disk storage system.
Recently, a computer system has been emerged in which a plurality of host computers shares a plurality of disk storage systems. In such a system, a network switch connects a plurality of disk storage systems to a plurality of host computers. For example, Japanese Patent Laid-open (Kokai) No. Hei 07-244642 discloses a system in which a host computer selects disk storage systems in compliance with a predetermined set of rules so as to evenly balance the load among them.
Most recently, an interface scheme called fibre channel has been proposed to communicate between a plurality of host computers and a plurality of disk storage systems with advantages, and is being spread. The fibre channel is a standard allowing a high speed packet communication similar to any other typical network. At the time of writing a computer system is advent, which uses a fibre channel switch for a router, packet routing device. FIG. 14 shows an exemplary system architecture of such system, which includes a plurality of host computers 102, 104 and 105 connected to a plurality of disk storage systems 106 and 107 through a storage network switch 101 for routing packets.